TV News July 2018

Commissioning AES67 in Your Plant

By now, you’ve heard that AES67 is part of the SMPTE 2110-30 standard and that all the major IP audio vendors offer this audio transport standard as part of their system.

The AES67 format will be useful for streaming audio between the control room and the master control and there’s good reason to believe that it will effectively eliminates the practice of HD/SDI audio embedding/de-embedding with video, and all the hardware that goes along with HD/SDI workflows.

There’s been a great deal of talk about AES67, but that is as far as it’s gone for most broadcasters – essentially a new standard still sitting on the dealer lot waiting for a test drive.

How easy will it be to commission AES67 in your plant?

We decided to take AES67 out for a spin to find out. Earlier this summer we did a trial run of AES67 through a large WheatNet-IP system staged at the Wheatstone factory in New Bern, North Carolina, during what we call a BLADEFest. (BLADEs are the I/O access units that make up the WheatNet-IP audio network). We do BLADEFests periodically to test our system under real-world conditions, and for this one, we added in a few AES67 devices while we were at it.

We added AES67 devices from Genelec, Ward-Beck, Dante, and Axia into the WheatNet-IP system of 12 mixing consoles, 62 hardware BLADEs (or I/O access units), 100 software BLADEs, talent stations, SideBoards, Smart Switch panels, and software including three different vendors’ automation systems. It was all tied together through Cisco and Dell switches.

We ran the system through a series of automated torture tests that included completely rebooting the system and verifying proper operation afterward. We’re happy to say that after more than 160 reboots, not a single connection failure or loss of audio occurred. We also learned a great deal about commissioning AES67 in a plant. Here are a few major findings.

Finding #1. To use AES67 devices, your system must have a PTPv2 clock reference device, preferably synced to GPS for absolute timing reference.

AES67 specifies version 2 of the IEEE-1588 Precision Time Protocol, or PTP, a protocol so precise that under ideal conditions, timing accuracy of better than 1 microsecond can be achieved. While some AES67 devices can provide PTP timing signals which might suffice for a small system, an ordinary crystal oscillator in a PC or I/O device is nowhere near accurate and stable enough to provide an absolute timing reference for a larger system, hence the need for standalone master clock generator.

For even greater timing accuracy you can use PTP compliant switches . These are significantly more expensive and are not needed for normal audio distribution, necessary only for applications that require absolute phase accuracy for audio signals distributed across complex networks with multiple switch hops.

Once the PTPv2 clock is running, it’s possible to begin connecting AES67 devices to the network.

Finding #2. Before connecting AES67 devices, map out an IP and stream multicast address plan with all devices on the same IP subnet. Each AoIP vendor has their own way of allocating addresses; a plan will assure there’s no overlap and that AES67 devices will be on the same IP subnet since multicasting does not normally cross subnet boundaries. Start with the AES67 devices that are least common or least flexible in specifying or changing multicast addresses.

Finding #3. When adding an AES67 device to the network, set the system sample rate at 48kHz unless you know the device sample rate. AES67 does not require devices to support 44.1kHz and many do not. You’ll most likely find this setting option and others in the admin software that comes with the network system. For example, the WheatNet-IP audio network uses Navigator, an interface screen of which is shown here.

Finding #4. When adding an AES67 device to the network, pay attention to packet timing incompatibilities.WheatNet-IP uses 1/4 ms packet timing for minimum latency. Most AES67 devices also support 1/4 ms packet timing but some, such as Dante, do not. For those devices that do not use 1/4 ms packet timing, we enabled the AES67 1 ms Support option in WheatNet-IP Navigator, as shown here.

Finding #5. Some AES67 devices do not offer an easy way to manually manage streaming details, although these devices often can read these details in the form of an SDP file.In our case, we created SDP files by simply right-clicking on the desired source stream’s name in the Navigator crosspoint grid and opening a window that let us create the file.

Overall, commissioning AES67 in most broadcast plants should be a nonevent as broadcasters begin adopting the SMPTE 2110 suite of standards.

Surprising Uses for AoIP

Oh, the places they go and the things that they do!

I/O BLADEs are the access units that form the WheatNet-IP audio network. But with audio mixing, processing, logic control and IP networking all in one rack unit, BLADEs can also be used for a number of interesting applications. Here are just a few:

Audio in the Outfield: Quickly set up a small studio at any sports venue. All you need is a BLADE at the press box as your audio interface into your mixing board and mics, and an Internet or other link to the studio. The BLADE gives you audio IP routing, processing, mixing and logic controls in one box.

IP Audio Snake: Transport audio between the production studio and a nearby performance studio using BLADEs at each end. Carry mic and instrument feeds from the stage area to the network over CAT6, wireless or optical fiber link. Do separate mixes live using the BLADE’s 8x2 stereo utility mixers or capture multitrack recordings for future mixing. No transformer splits required!

Multi-stage venues. Place BLADE I/O units in the van and on stages or throughout the field, and connect them together over fiber and CAT6 via the network switch for audio transport between them. Great for music festivals that require real-time communication between multiple stages.

IFB. Talk to talent over your IP network. BLADEs networked together provide the IFB pathway, whether it’s on location or in the studio. Simply change crosspoints using our NAVIGATOR software to create routable IFB throughout the facility.

Q: What is the difference between a distributed network like WheatNet-IP and the more traditional AoIP network?

A: Traditional AoIP networks are more centralized in how they control and manage audio. Nodes communicate directly with a central controller, where the core intelligence resides for the entire network. Distributed networks such as WheatNet-IP distribute intelligence to each of the I/O access units, which offers several benefits. Each I/O unit is capable, on its own, of getting things done, locally or anywhere else in the network. And because I/O devices communicate directly with each other, advanced routing of audio and logic becomes a simple matter and options open up for better automatic control of the network and its connected devices, as well as for communication with automation and playout systems. Setup and management are greatly simplified as well, and reliability is dramatically increased as many single-point failures are eliminated. In addition, because each network I/O device brings with it its own intelligence, scalability is assured because the system never runs out of processing power.

FREE E-BOOK: IP AUDIO FOR TV PRODUCTION AND BEYOND

Putting together a new studio? Updating an existing studio?

We've put together this IP Audio for TV Production and Beyond e-book with fresh info and some of the articles that we've authored for our website, white papers, and news that dives into some of the cool stuff you can do with a modern AoIP network like Wheatstone's WheatNet-IP. And it's FREE to download!

Rebooting A Giant WheatNet-IP System

Jay Tyler demonstrates just how robust a WheatNet-IP system can be. He reboots one of the largest systems out there and has the entire thing back up and running in 80 seconds. The system represents multiple studios spread across a facility and was commissioned by Cox Jacksonville.

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